Determination of nucleotides, nucleosides and their transformation products in Cordyceps by ion-pairing reversed-phase liquid chromatography–mass spectrometry

An ion-pairing reversed-phase liquid chromatography–mass spectrometry (IP-RP-LC–MS) was developed for the determination of nucleotides, nucleosides and their transformation products in Cordyceps. Perfluorinated carboxylic acid, namely pentadecafluorooctanoic acid (PDFOA, 0.25 mM), was used as volatile ion-paring agent and a reversed-phase column (Agilent ZORBAX SB-Aq column) was used for the separation of three nucleotides namely uridine-5′-monophosphate (UMP, 0.638–10.200 μg/mL), adenosine-5′-monophosphate (AMP, 0.24–7.80 μg/mL) and guanosine-5′-monophosphate (GMP, 0.42–13.50 μg/mL), seven nucleosides including adenosine (0.55–8.85 μg/mL), guanosine (0.42–6.75 μg/mL), uridine (0.33–10.50 μg/mL), inosine (0.21–6.60 μg/mL), cytidine (0.48–15.30 μg/mL), thymidine (0.20–6.30 μg/mL) and cordycepin (0.09–1.50 μg/mL), as well as six nucleobases, adenine (0.22–6.90 μg/mL), guanine (0.26–4.20 μg/mL), uracil (0.38–12.15 μg/mL), hypoxanthine (0.13–4.20 μg/mL), cytosine (0.39–12.45 μg/mL) and thymine (0.26–8.25 μg/mL) with 5-chlorocytosine arabinoside as the internal standard. The overall LODs and LOQs were between 0.01–0.16 μg/mL and 0.04–0.41 μg/mL for the 16 analytes, respectively. The contents of 16 investigated compounds in natural and cultured Cordyceps were also determined and compared after validation of the developed IP-RP-LC-MS method. The transformations of nucleotides and nucleosides in Cordyceps were evaluated based on the quantification of the investigated compounds in three extracts, including boiling water extraction (BWE), 24 h ambient temperature water immersion (ATWE) and 56 h ATWE extracts. Two transformation pathways including UMP → uridine → uracil and GMP → guanosine → guanine were proposed in both natural Cordyceps sinensis and cultured Cordyceps militaris. The pathway of AMP → adenosine → inosine → hypoxanthine was proposed in natural C. sinensis, while AMP → adenosine → adenine in cultured C. militaris. However, the transformation of nucleotides and nucleosides was not found in commercial cultured C. sinensis.